PASSENGERS on a Air New Zealand flight to Auckland had a scare when the plane lost pressure and rapidly descended.

The oxygen masks automatically deployed after the gradual loss of cabin pressure on the Boeing 737-300, which left Wellington on Friday morning, Air New Zealand chief flight operations and safety officer Captain David Morgan said.

“The pilots immediately initiated a descent to 7000 feet and the cabin crew advised passengers that oxygen masks were no longer required at that point.”

The plane landed without further incident, Mr Morgan said.

The plane was carrying 76 passengers and five crew, Air NZ said.

Air NZ engineers and the Transport Accident Investigation Commission are investigating (TAIC) why the plane lost pressure.

Air NZ had taken it out of service until the cause was discovered, TAIC chief investigator Tim Burfoot told AAP.

Two investigators had arrived in Auckland and were thoroughly looking over the plane, which may take a couple of days, he said.

“With a large passenger aircraft in an incident like this we’re always interested to find out what happened and why to try and stop it happening again in the future,” Mr Burfoot said.

MP Claudette Hauiti was on the flight and tweeted:

“Drama on#airnz414 well-Akld depressurisation oxygen Masks down passengers calm crew great all is well landed safely.”